Determining battery depletion for coordinating battery replacement

ABSTRACT

A power system within a battery-powered node includes a primary cell, a secondary cell, and a battery controller. The battery controller includes a constant current source that draws power from the primary cell to charge the secondary cell. The battery-powered node draws power from the secondary cell across a wide range of current levels. When the voltage of the secondary cell drops beneath a minimum voltage level, the constant current source charges the secondary cell and a charging signal is sent to the battery-powered node. When the voltage of the second cell exceeds a maximum voltage level, the constant current source stops charging the secondary cell and the charging signal is terminated. The battery-powered node records the amount of time the charging signal is active and then determines a battery depletion level based on that amount of time. Battery replacement may then be efficiently scheduled based on the depletion level.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of United States provisional patentapplication titled, “Battery Current Consumption Measurement,” filed onFeb. 6, 2017 and having Ser. No. 62/455,141. The subject matter of thisrelated application is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the present invention relate generally to wirelessnetwork communications and, more specifically, to determining batterydepletion for coordinating battery replacement.

Description of the Related Art

A conventional wireless mesh network includes a plurality of nodesconfigured to communicate with one another. In certain types ofheterogeneous wireless mesh networks, both continuously-powered nodesand battery-powered nodes communicate and interact with one anotherwithin the mesh network. Typically, continuously-powered nodes arecoupled to a power grid and have continuous access to power (exceptduring power outages). Battery-powered nodes, on the other hand, operatewith batteries that provide only a finite supply of power. To conservepower, battery-powered nodes may deactivate for long periods of time,during which little power is consumed, and then reactivate for shortperiods of time, during which very brief network communications areperformed. With this approach, a battery-powered node may operate with asingle battery for an extended period of time. When the batteryeventually becomes depleted, though, a service technician has to bedispatched to replace the battery.

Service technicians usually attempt to predict when battery-powerednodes will need replacement batteries based on a model of node powerconsumption. This approach confers at least two benefits. First, servicetechnicians can replace depleted batteries before those batteries arepredicted to expire, thereby minimizing or eliminating node downtime andpreserving network stability. Second, service technicians canconsolidate battery replacement assignments to occur on days whenmultiple nodes are predicted to need replacement batteries, therebyminimizing truck rolls.

That said, conventional battery-powered nodes usually consume power inan unpredictable manner due to the activation/reactivation behaviordescribed above. Therefore, predictions based on modeling, as discussedabove, are oftentimes inaccurate. To address this problem,battery-powered nodes can be equipped with battery monitors that reportbattery usage data to service technicians. Based on this usage data,service technicians can more efficiently schedule battery replacementassignments. However, implementing battery monitors with battery-powerednodes that operate over an extended period of time has at least twodrawbacks. First, a battery-powered node that operates according to theactivation/deactivation schedule discussed above typically consumespower over a wide range of currents during the short reactivationperiods. Power consumed over a wide range of currents cannot be measuredaccurately using a conventional battery monitor. Second, conventionalbattery monitors typically consume too much additional battery power,which can reduce the operational lifetime of a battery-powered nodebelow an acceptable timespan.

As the foregoing illustrates, what is needed in the art is a moreeffective way to determine battery depletion in power battery-powerednodes within a wireless mesh network.

SUMMARY OF THE INVENTION

One embodiment of the present invention sets forth acomputer-implemented method for determining battery depletion in abattery-powered node residing within a wireless mesh network, includingdetermining that a first voltage level associated with a secondary cellis less than a minimum voltage level, in response, activating a chargingsignal, conducting first electrical energy from a primary cell to thesecondary cell at a constant current level in response to the chargingsignal, where the battery-powered node draws second electrical energyfrom the secondary cell, and causing the battery-powered node to recorda first amount of time for which the charging signal is active, whereinthe first amount of time indicates a first amount of battery powerstored in the primary cell.

At least one advantage of the techniques described herein is thatbattery depletion can be reliably determined in battery-powered nodeswith extended operational lifetimes. Accordingly, the need to replacethe batteries in a given battery-powered node can be predicted withprecision

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 illustrates a network system configured to implement one or moreaspects of the present invention;

FIG. 2 illustrates a network interface configured to transmit andreceive data within the mesh network of FIG. 1, according to variousembodiments of the present invention;

FIG. 3 is a more detailed illustration of the power system of FIG. 2,according to various embodiments of the present invention;

FIG. 4 illustrates an exemplary implementation of the power system ofFIG. 3, according to various embodiments of the present invention; and

FIG. 5 is a flow diagram of method steps for determining batterydepletion within a battery-powered node, according to variousembodiments of the present invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a more thorough understanding of the present invention. However,it will be apparent to one of skill in the art that the presentinvention may be practiced without one or more of these specificdetails. In other instances, well-known features have not been describedin order to avoid obscuring the present invention.

As discussed above, battery-powered nodes that operate according to apunctuated activation/deactivation schedule oftentimes consume powerover a wide range of current levels. Conventional battery monitorscannot accurately measure power consumption over this wide range ofcurrents. Further, conventional battery monitors consume excessive powerand therefore may reduce the operational lifetime of the battery-powerednode below an acceptable timespan.

To address these issues, embodiments of the invention include abattery-powered node that draws power from a power system. The powersystem includes a primary cell and a secondary cell managed by a batterycontroller. The battery controller includes a constant current sourcethat draws power from the primary cell to charge the secondary cell. Thesecondary cell powers the battery-powered node, which may draw poweracross a wide range of current levels. When the voltage of the secondarycell drops beneath a minimum voltage level, the constant current sourcecharges the secondary cell and a charging signal is sent to thebattery-powered node. When the voltage of the second cell exceeds amaximum voltage level, the constant current source stops charging thesecondary cell and the charging signal is terminated. Thebattery-powered node records the amount of time the charging signal isactive and then determines a battery depletion level based on thatamount of time. The battery-powered node reports the depletion levelacross the network, thereby allowing battery replacement to beefficiently scheduled.

One advantage of the techniques described herein is that the batterycontroller can reliably indicate battery depletion in battery-powerednodes with extended operational lifetimes. Accordingly, the need toreplace the batteries in a given battery-powered node can be predictedwith precision. With such precision, service technicians can moreeffectively schedule battery replacements in a manner that minimizesnode downtime and minimizes truck rolls. Another advantage of thetechniques described herein is that the battery controller consumesminimal power and therefore does not significantly reduce theoperational lifespan of the battery powered node. For these reasons, thedisclosed approach represents a significant technical advancement.

System Overview

FIG. 1 illustrates a network system configured to implement one or moreaspects of the present invention. As shown, the network system 100includes a wireless mesh network 102, which may include a source node110, intermediate nodes 130 and destination node 112. The source node110 is able to communicate with certain intermediate nodes 130 viacommunication links 132. The intermediate nodes 130 communicate amongthemselves via communication links 134. The intermediate nodes 130communicate with the destination node 112 via communication links 136.The network system 100 may also include an access point 150, a network152, and a server 154. A given node 130 may be a continuously-powereddevice that is coupled to a power grid, or a battery-powered device thatincluded one or more internal batteries.

A discovery protocol may be implemented to determine node adjacency toone or more adjacent nodes. For example, intermediate node 130-2 mayexecute the discovery protocol to determine that nodes 110, 130-1,130-3, and 130-5 are adjacent to node 130-2. Furthermore, this nodeadjacency indicates that communication links 132-2, 134-2, 134-4 and134-3 may be established between the nodes 110, 130-1, 130-3, and 130-5,respectively. Any technically feasible discovery protocol may beimplemented without departing from the scope and spirit of embodimentsof the present invention.

The discovery protocol may also be implemented to determine the hoppingsequences of adjacent nodes, i.e. the sequence of channels across whichnodes periodically receive payload data. As is known in the art, a“channel” may correspond to a particular range of frequencies. Onceadjacency is established between the source node 110 and at least oneintermediate node 130, the source node 110 may generate payload data fordelivery to the destination node 112, assuming a path is available. Thepayload data may comprise an Internet protocol (IP) packet, or any othertechnically feasible unit of data. Similarly, any technically feasibleaddressing and forwarding techniques may be implemented to facilitatedelivery of the payload data from the source node 110 to the destinationnode 112. For example, the payload data may include a header fieldconfigured to include a destination address, such as an IP address ormedia access control (MAC) address.

Each intermediate node 130 may be configured to forward the payload databased on the destination address. Alternatively, the payload data mayinclude a header field configured to include at least one switch labelto define a predetermined path from the source node 110 to thedestination node 112. A forwarding database may be maintained by eachintermediate node 130 that indicates which communication link 132, 134,136 should be used and in what priority to transmit the payload data fordelivery to the destination node 112. The forwarding database mayrepresent multiple routes to the destination address, and each of themultiple routes may include one or more cost values. Any technicallyfeasible type of cost value may characterize a link or a route withinthe network system 100, although one specific approach is discussed ingreater detail below in conjunction with FIGS. 3A-5. In one embodiment,each node within the wireless mesh network 102 implements similarfunctionality and each node may act as a source node, destination nodeor intermediate node.

In network system 100, the access point 150 is configured to communicatewith at least one node within the wireless mesh network 102, such asintermediate node 130-4. Communication may include transmission ofpayload data, timing data, or any other technically relevant databetween the access point 150 and the at least one node within thewireless mesh network 102. For example, communications link 140 may beestablished between the access point 150 and intermediate node 130-4 tofacilitate transmission of payload data between wireless mesh network102 and network 152. The network 152 is coupled to the server 154 viacommunications link 142. The access point 150 is coupled to the network152, which may comprise any wired, optical, wireless, or hybrid networkconfigured to transmit payload data between the access point 150 and theserver 154.

In one embodiment, the server 154 represents a destination for payloaddata originating within the wireless mesh network 102 and a source ofpayload data destined for one or more nodes within the wireless meshnetwork 102. In one embodiment, the server 154 is a computing device,including a processor and memory, and executes an application forinteracting with nodes within the wireless mesh network 102. Forexample, nodes within the wireless mesh network 102 may performmeasurements to generate measurement data, such as power consumptiondata. The server 154 may execute an application to collect themeasurement data and report the measurement data. In one embodiment, theserver 154 queries nodes within the wireless mesh network 102 forcertain data. Each queried node replies with requested data, such asconsumption data, system status and health data, and so forth. In analternative embodiment, each node within the wireless mesh network 102autonomously reports certain data, which is collected by the server 154as the data becomes available via autonomous reporting.

The techniques described herein are sufficiently flexible to be utilizedwithin any technically feasible network environment including, withoutlimitation, a wide-area network (WAN) or a local-area network (LAN).Moreover, multiple network types may exist within a given network system100. For example, communications between two nodes 130 or between a node130 and the corresponding access point 150 may be via a radio-frequencylocal-area network (RF LAN), while communications between access points150 and the network may be via a WAN such as a general packet radioservice (GPRS). As mentioned above, each node within wireless meshnetwork 102 includes a network interface that enables the node tocommunicate wirelessly with other nodes. Each node 130 may implement anyand all embodiments of the invention by operation of the networkinterface. An exemplary network interface is described below inconjunction with FIG. 2.

FIG. 2 illustrates a network interface configured to transmit andreceive data within the mesh network of FIG. 1, according to variousembodiments of the present invention. Each node 110, 112, 130 within thewireless mesh network 102 of FIG. 1 includes at least a portion of thenetwork interface 200. As shown, the network interface 200 includes,without limitation, a microprocessor unit (MPU) 210, a digital signalprocessor (DSP) 214, digital to analog converters (DACs) 220, 221,analog to digital converters (ADCs) 222, 223, analog mixers 224, 225,226, 227, a phase shifter 232, an oscillator 230, a power amplifier (PA)242, a low noise amplifier (LNA) 240, an antenna switch 244, an antenna246, and a power system 250. Oscillator 230 may be coupled to a clockcircuit (not shown) configured to maintain an estimate of the currenttime. MPU 210 may be configured to update this time estimate, and otherdata associated with that time estimate.

A memory 212 may be coupled to the MPU 210 for local program and datastorage. Similarly, a memory 216 may be coupled to the DSP 214 for localprogram and data storage. Memory 212 and/or memory 216 may be used tobuffer incoming data as well as store data structures such as, e.g., aforwarding database, and/or routing tables that include primary andsecondary path information, path cost values, and so forth.

In one embodiment, the MPU 210 implements procedures for processing IPpackets transmitted or received as payload data by the network interface200. The procedures for processing the IP packets may include, withoutlimitation, wireless routing, encryption, authentication, protocoltranslation, and routing between and among different wireless and wirednetwork ports. In one embodiment, MPU 210 implements the techniquesperformed by the node when MPU 210 executes a firmware program stored inmemory within network interface 200.

The MPU 214 is coupled to DAC 220 and DAC 221. Each DAC 220, 221 isconfigured to convert a stream of outbound digital values into acorresponding analog signal. The outbound digital values are computed bythe signal processing procedures for modulating one or more channels.The DSP 214 is also coupled to ADC 222 and ADC 223. Each ADC 222, 223 isconfigured to sample and quantize an analog signal to generate a streamof inbound digital values. The inbound digital values are processed bythe signal processing procedures to demodulate and extract payload datafrom the inbound digital values.

In one embodiment, MPU 210 and/or DSP 214 are configured to bufferincoming data within memory 212 and/or memory 216. The incoming data maybe buffered in any technically feasible format, including, for example,raw soft bits from individual channels, demodulated bits, raw ADCsamples, and so forth. MPU 210 and/or DSP 214 may buffer within memory212 and/or memory 216 any portion of data received across the set ofchannels from which antenna 246 receives data, including all such data.MPU 210 and/or DSP 214 may then perform various operations with thebuffered data, including demodulation operations, decoding operations,and so forth.

MPU 210, DSP 214, and potentially other elements included in networkinterface 200 are powered by power system 250, as described in greaterdetail below in conjunction with FIGS. 3-5. Power system 250 includes ahigher voltage primary cell, such as a Lithium Thionyl Chloride (LTC)battery, and a lower voltage secondary cell, such as a Lithium Ion(Li-ion) battery. Power system 250 also includes a battery controllerthat charges the secondary cell with a constant current that is derivedfrom the primary cell. During charging of the secondary cell, thebattery controller outputs a charging signal to accumulator 252.Accumulator 252 records the activity of the charging signal over time togenerate charging data. For example, accumulator 252 could record thetotal amount of time that the charging signal is active. Accumulator 252transmits the charging data to MPU 210, and MPU 210 may then report thisdata upstream to server 154. MPU 210 may also process the charging datato determine a battery depletion level and/or a date and time ofcomplete battery depletion. MPU 210 may then report this data to server154. In one embodiment, MPU 210 includes a software implementation ofaccumulator 252.

One advantage of the above approach is that based on the charging data,a service technician can accurately determine when a given node 130 willneed replacement batteries, thereby allowing the technician to minimizenode downtime and minimize truck rolls.

Persons having ordinary skill in the art will recognize that networkinterface 200 represents just one possible network interface that may beimplemented within wireless mesh network 102 shown in FIG. 1, and thatany other technically feasible device for transmitting and receivingdata may be incorporated within any of the nodes within wireless meshnetwork 102.

Measuring Battery Depletion in Battery-Powered Nodes

FIG. 3 is a more detailed illustration of the power system of FIG. 2,according to various embodiments of the present invention. As shown,power system 250 includes a battery controller 300 coupled between aprimary cell 310 and a secondary cell 330. Battery controller 300includes a constant current source 302 and a voltage monitor 304.

Primary cell 310 may deliver charge at greater than 3.6 Volts and may bea lithium thionyl chloride (LTC) battery. Secondary cell 330 generallydelivers charge at less than 3.6 Volts, and may be a lithium ion(Li-ion) battery. Secondary cell 330 powers load 340. Secondary cell 330may have a low impedance, thereby allowing load 340 to draw power acrossa wide range of currents during a short time scale. Load 340 may includesome or all elements included in network interface 200 of FIG. 2, suchas accumulator 252, as is shown. The maximum operating voltage of load340 may be less than 3.6 Volts.

In operation, voltage monitor 304 monitors a voltage level associatedwith secondary cell 330 and then toggles a charging signal when thatvoltage level reaches specific thresholds. In particular, when thevoltage level of secondary cell 330 decreases to less than a minimumvoltage level, voltage monitor 304 activates the charging signal. Whenthe voltage level of secondary cell 330 increases to greater than amaximum voltage level, voltage monitor 304 deactivates the chargingsignal. The minimum and maximum threshold values may be derived fromcharacteristics of load 340, such as minimum and maximum operatingvoltages.

When the charging signal is active, constant current source 302 isenabled and draws electrical energy from primary cell 310. Constantcurrent source 302 transmits this electrical energy to secondary cell330 at a constant (and potentially fixed) current level, therebycharging secondary cell 330. Accumulator 252 records the activity ofcharging signal over time to generate charging data. When the chargingsignal is not active, constant current source 302 is not enabled anddoes not draw electrical energy from primary cell 310. Accumulator 252may record that the charging signal is not active or may stop recordingdata. Load 340 may continue to draw electrical energy from secondarycell 330. When the voltage level associated with secondary cell 330decreases beneath the minimum voltage level, charging may commenceagain, and the charging signal may be reactivated.

With the configuration of cells discussed herein, depletion of primarycell 310 can be accurately determined based on the charging signalbecause electrical energy is drawn from that cell at a specific,constant current level. For example, the constant current level could bemultiplied by the total charging time to compute the total number of AmpSeconds drawn from primary cell 310. Based on this data and based on aninitial charge capacity of primary cell 310, the depletion level ofprimary cell 310 at any given time can be determined. Further, becausethe electrical energy drawn from primary cell 310 is subsequently storedin secondary cell 330, load 340 may draw power from secondary cell 330across a wide range of current levels. Accordingly, the disclosedapproach resolves a specific technical issue associated withconventional battery monitors that cannot accurately measure batterydepletion in battery-powered nodes that draw power across a wide rangeof current levels.

Persons skilled in the art will recognize that the above-describedtechnique for charging secondary cell 330 via primary cell 310 confersimportant advantages apart from the ability to accurately measurebattery depletion. In particular, primary cell 310 may be a highervoltage battery (such as an LTC battery) that delivers electrical energyat a voltage exceeding the maximum operating voltage of load 340.Although this type of battery may have an extended lifetime, integratedcircuitry within a conventional battery-powered node would be damaged bythese higher voltage levels.

With the approach described above, though, primary cell 310 may beelectrically isolated from load 340 and only used to charge secondarycell 330. Secondary cell 330, in turn, may provide electrical energy toload 340 at a voltage that does not exceed the maximum operating voltageof load 340. Accordingly, the disclosed approach allows a higher voltagebattery with an extended lifespan to power lower voltage circuitry suchas network interface 200.

FIG. 4 illustrates an exemplary implementation of the power system ofFIG. 3, according to various embodiments of the present invention. Asshown, battery controller 300 includes numerous electronic elementscoupled together and coupled to primary cell 310, secondary cell 330,and load 340. Certain elements shown can be used to implement constantcurrent source 302 and voltage monitor 304 discussed above inconjunction with FIG. 3.

Constant current source 302 may be implemented using operationalamplifier (op-amp) U10. Op-amp U10 senses current through resistor R72and controls current flowing through metal-oxide-semiconductorfield-effect transistor (MOSFET) Q6. The current flowing through MOSFETQ6 can be modified by adjusting the resistance of resistor R69. Personsskilled in the art will understand that any of the other elements shownin FIG. 4 may be included in constant current source 302.

Voltage monitor 304 may be implemented using a comparator U12 or anyother type of low power device with a voltage reference than can be usedto control the charge voltage on another device. Comparator U12 may havebuilt-in hysteresis to limit the rate of current fluctuations. In oneembodiment, comparator U12 may output the charging signal to accumulator252 as PW1.

In operation, comparator U12 monitors the voltage across secondary cell330 and then transmits the charging signal when that voltage decreasesbeneath a minimum threshold value. In response, MOSFET Q6 interoperateswith MOSFET Q8 to electrically couple primary cell 310 to secondary cell330, thereby charging secondary cell 330 with electrical energy derivedfrom primary cell 310 at a constant current level. Subsequently, whenthe voltage across secondary cell 330 increases to exceed the maximumvoltage, comparator U12 disables the charging signal, thereby causingMOSFETs Q6 and Q8 to electrically decouple secondary cell 330 fromprimary cell 310.

As mentioned, the circuit shown in FIG. 4 is provided for exemplarypurposes to illustrate one possible implementation of battery controller300. Other implementations also fall within the scope of the variousembodiments. The techniques performed via battery controller 300 aredescribed in stepwise fashion below in conjunction with FIG. 5.

FIG. 5 is a flow diagram of method steps for monitoring batterydepletion within a battery-powered node, according to variousembodiments of the present invention. Although the method steps aredescribed in conjunction with the systems of FIGS. 1-4, persons skilledin the art will understand that any system configured to perform themethod steps, in any order, is within the scope of the presentinvention.

As shown, a method 500 begins at step 502, where battery controller 300charges secondary cell 330 with constant current source 302 driven byprimary cell 310. Primary cell 310 may provide a voltage that exceedsthe maximum operating voltage of load 340. At step 504, batterycontroller 300 causes load 340 to record that constant current source302 is active and depleting energy stored by primary cell 310. Inperforming step 504, battery controller 300 transmits the chargingsignal to load 340. At step 506, battery controller 300 determines thatthe voltage of secondary cell 330 is greater than a maximum voltagevalue. The maximum voltage value may be derived from the maximum loadvoltage associated with load 340.

At step 508, battery controller 300 deactivates constant current source302 to stop charging secondary cell 330. At step 510, battery controller300 causes load 340 to record that constant current source 302 is notactive and not depleting energy stored by primary cell 310. Inperforming step 510, battery controller 300 stops transmitting thecharging signal to load 340. At step, 512 battery controller 300determines that the voltage of secondary cell 330 is less than a minimumvoltage value. The minimum voltage value may be derived from the minimumload voltage associated with load 340. The method may then return tostep 502 and repeat.

By implementing the method 500, battery controller 300 is capable ofcausing a battery-powered node to record precise consumption data thatreflects an amount of energy depleted from batteries during nodeoperations. The battery-powered node may also compute an estimated dateand time when batteries will deplete entirely, potentially leading tonode deactivation. The battery-powered node may provide this data toserver 154 in response to a query. By querying many battery-powerednodes in this manner, server 154 may determine a subset of those nodesthat may soon lose power due to battery depletion. One or more servicetechnicians can then be scheduled to replace the batteries in thosenodes, thereby maintaining network stability.

In sum, a battery-powered node draws power from a power system. Thepower system includes a primary cell and a secondary cell managed by abattery controller. The battery controller includes a constant currentsource that draws power from the primary cell to charge the secondarycell. The secondary cell powers the battery-powered node across a widerange of current levels. When the voltage of the secondary cell dropsbeneath a minimum voltage level, the constant current source charges thesecondary cell and a charging signal is sent to the battery-powerednode. When the voltage of the second cell exceeds a maximum voltagelevel, the constant current source stops charging the secondary cell andthe charging signal is terminated. The battery-powered node records theamount of time the charging signal is active and then determines abattery depletion level based on that amount of time. Thebattery-powered node reports the depletion level across the network,thereby allowing battery replacement to be efficiently scheduled.

One advantage of the techniques described herein is that the batterycontroller can reliably indicate battery depletion in battery-powerednodes with extended operational lifetimes. Accordingly, the need toreplace the batteries in a given battery-powered node can be predictedwith precision. With such precision, service technicians can moreeffectively schedule battery replacements in a manner that minimizesnode downtime and minimizes truck rolls. Another advantage of thetechniques described herein is that the battery controller consumesminimal power and therefore does not significantly reduce theoperational lifespan of the battery powered node. For at least thesereasons, the disclosed approach represents a significant technicaladvancement relative to prior art solutions.

1. Some embodiments include a computer-implemented method fordetermining battery depletion in a battery-powered node residing withina wireless mesh network, the method comprising: determining that a firstvoltage level associated with a secondary cell is less than a minimumvoltage level, in response, activating a charging signal, conductingfirst electrical energy from a primary cell to the secondary cell at aconstant current level in response to the charging signal, wherein thebattery-powered node draws second electrical energy from the secondarycell, and causing the battery-powered node to record a first amount oftime for which the charging signal is active, wherein the first amountof time indicates a first amount of battery power stored in the primarycell.

2. The computer-implemented method of clause 1, wherein the minimumvoltage level corresponds to a minimum operating voltage associated withthe battery-powered node.

3. The computer-implemented method of any of clauses 1 and 2, furthercomprising: determining that a second voltage level associated with thesecondary cell is greater than a maximum voltage level, in response,deactivating the charging signal, electrically isolating the primarycell from the secondary cell once the charging signal is deactivated,and causing the battery powered node to not record any information aboutthe charging signal.

4. The computer-implemented method of any of clauses 1, 2, and 3,wherein the maximum voltage level corresponds to a maximum operatingvoltage associated with the battery-powered node.

5. The computer-implemented method of any of clauses 1, 2, 3, and 4,wherein conducting the first electrical energy from the primary cell tothe secondary cell comprises enabling, via the charging signal, aconstant current source coupled between the primary cell and thesecondary cell.

6. The computer-implemented method of any of clauses 1, 2, 3, 4, and 5,wherein the primary cell comprises a lithium thionyl chloride batterythat outputs electrical energy with a voltage level that is greater thana maximum operating voltage associated with the battery-powered node.

7. The computer-implemented method of any of clauses 1, 2, 3, 4, 5, and6, wherein the secondary cell comprises a lithium ion battery thatoutputs electrical energy with a voltage level that is less than amaximum operating voltage associated with the battery-powered node.

8. The computer-implemented method of any of clauses 1, 2, 3, 4, 5, 6,and 7, further comprising reporting the first amount of battery power toa server machine configured to manage the wireless mesh network.

9. The computer-implemented method of any of clauses 1, 2, 3, 4, 5, 6,7, and 8, further comprising computing an estimated date and time whenthe first primary cell will be depleted based on the first amount oftime and reports the estimated date and time to a server machineconfigured to manage the wireless mesh network.

10. The computer-implemented method of any of clauses 1, 2, 3, 4, 5, 6,7, 8, and 9, further comprising drawing the second electrical energyfrom the secondary cell to perform wireless communications with one ormore other nodes residing in the wireless mesh network.

11. Some embodiments include a system for determining battery depletionin a battery-powered node residing within a wireless mesh network,comprising: a voltage monitor that: determines that a first voltagelevel associated with a secondary cell is less than a minimum voltagelevel, in response, activates a charging signal, and causes thebattery-powered node to record a first amount of time for which thecharging signal is active, wherein the first amount of time indicates afirst amount of battery power stored in a primary cell, and a constantcurrent source that conducts first electrical energy from the primarycell to the secondary cell in response to the charging signal, whereinthe battery-powered node draws second electrical energy from thesecondary cell.

12. The system of clause 11, wherein the minimum voltage levelcorresponds to a minimum operating voltage associated with thebattery-powered node.

13. The system of any of clauses 11 and 12, wherein the voltage monitordetermines that a second voltage level associated with the secondarycell is greater than a maximum voltage level and, in response,deactivates the charging signal,

14. The system of any of clauses 11, 12, and 13, wherein the constantcurrent source electrically isolates the primary cell from the secondarycell once the charging signal is deactivated, wherein the batterypowered node does not record any information about the charging signalwhen the charging signal is deactivated.

15. The system of any of clauses 11, 12, 13, and 14, wherein the maximumvoltage level corresponds to a maximum operating voltage associated withthe battery-powered node.

16. The system of any of clauses 11, 12, 13, 14, and 15, wherein theprimary cell comprises a lithium thionyl chloride battery that outputselectrical energy with a voltage level that is greater than a maximumoperating voltage associated with the battery-powered node, and whereinthe secondary cell comprises a lithium ion battery that outputselectrical energy with a voltage level that is less than the maximumoperating voltage associated with the battery-powered node.

17. The system of any of clauses 11, 12, 13, 14, 15, and 16, wherein thebattery-powered node computes an estimated date and time when the firstprimary cell will be depleted based on the first amount of time andreports the estimated date and time to a server machine configured tomanage the wireless mesh network.

18. The system of any of clauses 11, 12, 13, 14, 15, 16, and 17, whereinthe battery-powered node draws the second electrical energy from thesecondary cell to perform wireless communications with one or more othernodes residing in the wireless mesh network.

19. The system of any of clauses 11, 12, 13, 14, 15, 16, 17, and 18,wherein the battery-powered node activates during a first recurring timeperiod to perform the wireless communications with the one or more othernodes, and wherein the battery-powered node draws the second electricalenergy from the secondary cell across a first range of current levelsduring the first recurring time period.

20. The system of any of clauses 11, 12, 13, 14, 15, 16, 17, 18, and 19,wherein the primary cell cannot output electrical energy across thefirst range of current levels during the first recurring time period.

Any and all combinations of any of the claim elements recited in any ofthe claims and/or any elements described in this application, in anyfashion, fall within the contemplated scope of the present invention andprotection.

The descriptions of the various embodiments have been presented forpurposes of illustration, but are not intended to be exhaustive orlimited to the embodiments disclosed. Many modifications and variationswill be apparent to those of ordinary skill in the art without departingfrom the scope and spirit of the described embodiments.

Aspects of the present embodiments may be embodied as a system, methodor computer program product. Accordingly, aspects of the presentdisclosure may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects that may all generally be referred to herein as a “module” or“system.” Furthermore, aspects of the present disclosure may take theform of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

Aspects of the present disclosure are described above with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of thedisclosure. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, enable the implementation of the functions/acts specified inthe flowchart and/or block diagram block or blocks. Such processors maybe, without limitation, general purpose processors, special-purposeprocessors, application-specific processors, or field-programmableprocessors.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present disclosure. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblocks may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While the preceding is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

The invention claimed is:
 1. A computer-implemented method fordetermining battery depletion in a battery-powered node residing withina wireless mesh network, the method comprising: determining that a firstvoltage level associated with a secondary cell is less than a minimumvoltage level, in response, activating a charging signal; conductingfirst electrical energy from a primary cell to the secondary cell at aconstant current level in response to the charging signal, wherein thebattery-powered node draws second electrical energy from the secondarycell; and causing the battery-powered node to record a first amount oftime for which the charging signal is active, wherein the first amountof time indicates a first amount of battery power stored in the primarycell.
 2. The computer-implemented method of claim 1, wherein the minimumvoltage level corresponds to a minimum operating voltage associated withthe battery-powered node.
 3. The computer-implemented method of claim 1,further comprising: determining that a second voltage level associatedwith the secondary cell is greater than a maximum voltage level; inresponse, deactivating the charging signal; electrically isolating theprimary cell from the secondary cell once the charging signal isdeactivated; and causing the battery powered node to not record anyinformation about the charging signal.
 4. The computer-implementedmethod of claim 3, wherein the maximum voltage level corresponds to amaximum operating voltage associated with the battery-powered node. 5.The computer-implemented method of claim 1, wherein conducting the firstelectrical energy from the primary cell to the secondary cell comprisesenabling, via the charging signal, a constant current source coupledbetween the primary cell and the secondary cell.
 6. Thecomputer-implemented method of claim 1, wherein the primary cellcomprises a lithium thionyl chloride battery that outputs electricalenergy with a voltage level that is greater than a maximum operatingvoltage associated with the battery-powered node.
 7. Thecomputer-implemented method of claim 1, wherein the secondary cellcomprises a lithium ion battery that outputs electrical energy with avoltage level that is less than a maximum operating voltage associatedwith the battery-powered node.
 8. The computer-implemented method ofclaim 1, further comprising reporting the first amount of battery powerto a server machine configured to manage the wireless mesh network. 9.The computer-implemented method of claim 1, further comprising computingan estimated date and time when the first primary cell will be depletedbased on the first amount of time and reports the estimated date andtime to a server machine configured to manage the wireless mesh network.10. The computer-implemented method of claim 1, further comprisingdrawing the second electrical energy from the secondary cell to performwireless communications with one or more other nodes residing in thewireless mesh network.
 11. A system for determining battery depletion ina battery-powered node residing within a wireless mesh network,comprising: a voltage monitor that: determines that a first voltagelevel associated with a secondary cell is less than a minimum voltagelevel, in response, activates a charging signal, and causes thebattery-powered node to record a first amount of time for which thecharging signal is active, wherein the first amount of time indicates afirst amount of battery power stored in a primary cell; and a constantcurrent source that conducts first electrical energy from the primarycell to the secondary cell in response to the charging signal, whereinthe battery-powered node draws second electrical energy from thesecondary cell.
 12. The system of claim 11, wherein the minimum voltagelevel corresponds to a minimum operating voltage associated with thebattery-powered node.
 13. The system of claim 11, wherein the voltagemonitor determines that a second voltage level associated with thesecondary cell is greater than a maximum voltage level and, in response,deactivates the charging signal;
 14. The system of claim 13, wherein theconstant current source electrically isolates the primary cell from thesecondary cell once the charging signal is deactivated, wherein thebattery powered node does not record any information about the chargingsignal when the charging signal is deactivated.
 15. The system of claim13, wherein the maximum voltage level corresponds to a maximum operatingvoltage associated with the battery-powered node.
 16. The system ofclaim 11, wherein the primary cell comprises a lithium thionyl chloridebattery that outputs electrical energy with a voltage level that isgreater than a maximum operating voltage associated with thebattery-powered node, and wherein the secondary cell comprises a lithiumion battery that outputs electrical energy with a voltage level that isless than the maximum operating voltage associated with thebattery-powered node.
 17. The system of claim 11, wherein thebattery-powered node computes an estimated date and time when the firstprimary cell will be depleted based on the first amount of time andreports the estimated date and time to a server machine configured tomanage the wireless mesh network.
 18. The system of claim 11, whereinthe battery-powered node draws the second electrical energy from thesecondary cell to perform wireless communications with one or more othernodes residing in the wireless mesh network.
 19. The system of claim 11,wherein the battery-powered node activates during a first recurring timeperiod to perform the wireless communications with the one or more othernodes, and wherein the battery-powered node draws the second electricalenergy from the secondary cell across a first range of current levelsduring the first recurring time period.
 20. The system of claim 19,wherein the primary cell cannot output electrical energy across thefirst range of current levels during the first recurring time period.